There is a recurring question about these kinds of numbers. What if it is “…sent a hundred dollars to him” or “…paid ten and a half” or “…a little over a million”? The answer is that these are technically not really numbers — “a million” and “a half” and “a hundred.” And English rules say that these should be written out in words since they are not really numbers.
The dilemma, of course, is that, when these are mixed in with regular numbers, writing them in words does not always “fit” with the transcript form. What if it is “…paid $895,000 for it and sold it for a million”? There is a consistency issue.
So what is the answer? You are probably not going to like this. The answer is that you must decide whether you want to be totally verbatim and keep the “a” in lieu of the “one.” OR you decide that you are going to go ahead and write the number in figures as if it had been said with the word “one.”
If you write it in words, then every part of it has to be in words.
…spent a hundred and fifteen dollars on that.
The choice is yours.